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3A 12v regulator?

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  • 3A 12v regulator?

    If I can find plans or make plans for a 3A 12v regulator that will work from 9-18v input that would be great. The idea is to use a mini itx mother board + the pw-120-m. Sence the mini itx mobo dosnt use the 12v rail then I don't need to worie about that part. I just need a small 12v regulator so I can use full size hard drive and cd rom. I'm planing on puting the 12v regulator after the pw-120-m. So if any one has any plans that would be super great.

  • #2
    Originally posted by hcker2000
    If I can find plans or make plans for a 3A 12v regulator that will work from 9-18v input that would be great. The idea is to use a mini itx mother board + the pw-120-m. Sence the mini itx mobo dosnt use the 12v rail then I don't need to worie about that part. I just need a small 12v regulator so I can use full size hard drive and cd rom. I'm planing on puting the 12v regulator after the pw-120-m. So if any one has any plans that would be super great.
    see if you can find 3 pieces of the UM2702 (Universal Microelectronics)
    http://www.umec-web.net/

    each puts out about 1.25A. it retails for 18 SGD (about 10USD) each in singapore.

    that's the easiers way for me so far. I used it to power devices that are too far from the PSU to be run the power cable. I hacked the USB cable to run 12V through it (on both end) and run one of these babies to give me instant 12V & 5V. 5V sees too much drop when you run it through long USB cables.

    kao
    ***
    CarPC Ver 4 completed. Aopen i45GMT-HD, C2D mobile 2GHz. Photofast 64GB SSD. Novatel EU-850D

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    • #3
      Thanks for the info I'll keep those in mind. I'm hoping I can find a solution with a total cost of around $15 or so. Basicly just need enough to run a full size cd rom and hard drive.

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      • #4
        Natsemi has this nice IC.

        http://www.national.com/pf/LM/LM1084.html

        I've used them a couple of times, nice and easy and do up to 5A (a bit more if you heatsink them well). 1.3V drop out. A bit expensive to buy in small quantities, but they ship free samples to many countries.

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        • #5
          ... or combine 2 pcs. of 7812s (the S is for 2A) ... they cost next to nothing

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          • #6
            Ok will LM1084 be able to out put 12v if the input falls below 12v?

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            • #7
              No it won't. If people would read what others have posted rather than jumping at the chance to be a hero and offer what they think is great advice it would save a lot of trouble.

              What you want to do plenty of people are trying to work on. Regulating the 12V line in a car environment isn't easy and it won't be easy for you if you don't have more than basic knowledge of circuits.

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              • #8
                Ah sorry i missed the 9-18V bit, thought he just wanted a 12V post regulator.

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                • #9
                  use two TI PT5071 regulators with the outputs connected in parallel via schottkey diodes. I use four of these in parallel and it has worked great for almost two years.
                  My Celica Carputer Install

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                  • #10
                    EBJUSTIN: dose it work when the car is runing and when the car is off? Also how many amp can it handle? and do you have a quick layout of the components?

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                    • #11
                      Originally posted by hcker2000
                      EBJUSTIN: dose it work when the car is runing and when the car is off? Also how many amp can it handle? and do you have a quick layout of the components?
                      Each PT 5071 module is rated at 1.5A. Yes it will provide a constant 12V with the car off, during crank and with the car on since it's input requirements are 7-16V.

                      You can find schematics here. This doesn't need to be real complicated. Just place a couple caps at the inputs and outputs and place a schottkey diode in series with each output. The output voltage will be a little less than 12V due to the diode drop but should stay above 12V. The actual voltage drop across the diode is determined by temperature and the amount of current draw.
                      My Celica Carputer Install

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                      • #12
                        I'm intending to try using a $10 7.2Ah sealed lead acid battery and some diodes with a PW-200-V.

                        Switched 12V car -> diode -> battery -> diode -> diode -> PW-200-V

                        In my car, the switched 12V is off during the crank. Is around 13.8->14.5V during drive and around 11.8V after I've switched the engine off but not fully switched the ignition off.

                        The tank battery should keep the output around (13.8-14.5) - 0.6 * 3 = 12->12.7V.

                        I'm going to get the diodes and battery today to see whether the output voltage looks good.
                        Progress: 80% - Permanent install left.
                        Motion LS800 Tablet PC and dock.
                        Vista, Bu-535 GPS, RoadRunner, MPT2006.

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